References.

[1] Thompson J.D., Higgins D.G. and Gibson T.J. CLUSTAL W: improving the sensitivity of progressive multiple sequence alignment through sequence weighting, positions-specific gap penalties and weight matrix choice.  Nucl. Acids Res. 1994. V. 22. P. 4673-4680.

[2] Altsñhul S.F., Carroll R.J. and Lipman D.J. Weights for data related by a tree.  J. Mol. Biol. 1989. V. 207. P. 647-653.

[3] Kissinger C.R., Liu B., Martin-Blanco E., Kornberg T.B. and Pabo C.O. Crystal structure of an engrailed homeodomain-DNA complex at 2.8 A resolution: a framework for understanding homeodomain-DNA interactions.  Cell. 1990. V. 63. P. 579-590.

[4] Clarke,N.D. (1995) Covariation of residues in homeodomain sequence family. Prot. Sci., 4, 2269-2278.